During the production of metallic moldings in the foundry, liquid metal is poured into a mold where it then solidifies. The solidification procedure is associated with a reduction in the metal volume and for this reason, feeders, i.e. open or closed spaces in or on the mold are routinely used in order to compensate for the deficit in volume when the cast part solidifies and to thus prevent a shrinkage cavity from forming in the cast part. Feeders are associated with the cast part or with the cast part region which is at risk and are usually located above and/or on the side of the mold cavity.
In feeder compositions for the production of feeders and in the feeders themselves produced therefrom, light fillers are regularly used today which should produce a good insulating effect with a high temperature resistance.
DE 10 2005 025 771 B3 discloses insulating feeders comprising ceramic hollow spheres and glass hollow spheres.
EP 0 888 199 B1 describes feeders which contain hollow aluminum silicate microspheres as an insulating fire-resistant material.
EP 0 913 215 B1 discloses feeder compositions which comprise hollow aluminum silicate microspheres having an aluminum oxide content of less than 38% by weight.
WO 9423865 A1 discloses a feeder composition comprising hollow microspheres containing aluminum oxide with an aluminum oxide proportion of at least 40% by weight.
WO 2006/058347 A2 discloses feeder compositions which comprise as fillers core-sheath microspheres with a polystyrene core. However, the use of polystyrene results in undesirable emissions during casting.